The invention relates to a continuous processing method and a continuous processing apparatus for continuously carrying out deactivation and sterilization processes of enzymes and spores of liquid-form foods and liquid-form medical supplies, or deodorization process of the liquid-form foods or the like, by using a supercritical or subcritical fluid, and a liquid substance, such as liquid-form food or drink and liquid-form medical supply, obtained by the above method and apparatus.
There are various kinds of liquid-form foods containing enzymes, typically such as refined sake, beer and fruit juice. A manufacturing process of the refined sake includes a first step wherein young sake is obtained by carrying out compression and filtration after completion of a fermentation; a second step wherein the obtained young sake is heated and sterilized, and then stored; a third step wherein the obtained original sake is mixed to determine its quality, and at the same time, to allow its alcoholic content to match the standard; and a fourth step wherein the adjusted sake is again heated to sterilize and filled in a bottle or a paper pack. As described above, in the refined sake which has been subjected to two times of heating processes, the enzymes are deactivated and sterilized, so that the quality of the refined sake during its distribution can be prevented from being deteriorated. However, such a heating process extremely reduces a fresh flavor and taste of the young sake. Therefore, in order to enjoy such fresh flavor and taste, there has been produced a green or fresh sake wherein the heating process is not carried out. The fresh sake is distributed at a cold temperature in order to protect its quality. However, such a fresh sake which has not been subjected to the heating process is liable to deteriorate in its quality due to actions of enzymes, such as an xcex1-amylase, protease or the like. Further, there is a problem that its cost is raised because of the cold temperature distribution.
Also, in order to keep a stability of a turbid juice, such as orange juice, inactivation of pectinesterase is required. Since the pectinesterase is a stable enzyme against heat, in order to carry out inactivation of the pectinesterase by heating, a heat process under the condition of a high temperature in the order of 88 to 99xc2x0 C. or 120xc2x0 C., is required. However, when the heat process under such a high temperature is carried out, the flavor of the juice may be deteriorated.
In view of the problems as described above, the present inventors have already proposed a novel technique wherein an enzyme contained in a liquid-form food is subjected to contact with a supercritical state carbon dioxide to thereby deactivate the enzymes (Japanese Patent Publication (KOKAI) 7-170965). According to the technique, an enzyme contained in the liquid-form food is stored in a process tank and sealed; an interior of the sealed tank is held under the condition of a predetermined temperature and pressure; and a supercritical fluid of carbon dioxide is supplied into the process tank through a filter to form a fine size, i.e. average diameter less than several hundreds xcexcm, so that the supercritical fluid can be easily dissolved in the liquid-form food. According to the method, enzyme can be effectively deactivated, and at the same time, since only carbon dioxide contacts the food, there is an advantage that a high safety can be obtained. Also, according to the method, microorganisms, such as bacteria, yeast and mold, can be sterilized at the same time.
Further, the present inventors have proposed a continuous processing apparatus for carrying out the deactivation and sterilization process effectively without deterioration of quality of products (Japanese Patent Publication (KOKAI) 9-206044, U.S. Pat. No. 5,704,276). In the continuous processing apparatus, a liquid-form food is continuously supplied to a bottom portion of the process tank held at a predetermined pressure and temperature; at the same time, supercritical state carbon dioxide is continuously supplied to the bottom portion of the process tank through a mesh-type filter disposed thereat; and a liquid outlet is provided at an upper portion of the process tank in the vicinity under a liquid-surface to thereby collect a product. The liquid-form food and the fine bubble-form supercritical fluid contact each other while making a parallel flow in an elevating direction in the process tank to thereby effectively deactivate enzymes. Also, a supercritical fluid discharge port is disposed at an upper portion of the process tank, through which the supercritical fluid is taken out and returned to a carbon dioxide supply source to reuse. According to the apparatus, since the liquid-form food can be continuously processed, the apparatus is suitable for a factory which processes a large amount of drinks or foods.
According to the above explained continuous processing apparatus, the deactivation and sterilization process of enzymes can be continuously carried out highly efficiently. However, in case the continuous processing apparatus is to be used practically, there is a problem, especially, in its cost. More specifically, in the above continuous processing apparatus, it is required that the process tank is held at a temperature higher than 31.1xc2x0 C. in order to hold carbon dioxide in a supercritical state. However, a solubility of carbon dioxide into the liquid-form food becomes lower as the temperature becomes higher. Thus, in view of dissolution, its efficiency is poor. Therefore, in order to obtain sufficient deactivation and sterilization effects, it is required that the liquid-form food and the supercritical fluid are subjected to a parallel flow for a predetermined time in the order of several to several tens of minutes. Therefore, it is necessary to shorten time by making the process tank in a large capacity. Also, in order to hold the process tank at the above-stated temperature, it is required to provide a heater. Further, since a reaction in the process tank becomes slow when a temperature of the liquid-form food supplied to the process tank is low, a heater for properly heating the liquid-form food is required before the food is supplied to the process tank. As described above, the continuous process apparatus requires an equipment on a large scale, which results in a large occupancy area as well as a high cost.
Also, the temperature in the process tank is considerably lower than that for deactivating enzymes by heating, but higher than the room temperature. Thus, in case the liquid-form food is left as it is under such a temperature condition for the predetermined time, the quality of the liquid-form food may be deteriorated. More specifically, for example, a citrus juice right after squeezed contains high active enzymes, so that the enzymes may act on the juice in the process tank before the enzymes are deactivated to deteriorate a quality of the juice.
To solve these problems, the present invention has been made, and an object of the invention is to provide a continuous processing method, a continuous processing apparatus and a liquid-form substance processed thereby, wherein a process tank can be miniaturized and the number of heaters to be disposed can be minimized.
Further objects and advantages of the invention will be apparent from the following description of the invention.
In the continuous processing apparatus disclosed in the previous application, a step for dissolving carbon dioxide in a liquid-form food and a step for allowing carbon dioxide to be a supercritical state and holding in its state, are carried out in a process tank simultaneously. On the contrary, in a continuous processing method and a continuous processing apparatus according to the present invention for solving the above problems, two processes disclosed in the previous application are carried out separately timewise and spacewise.
More specifically, in the continuous processing method according to the present invention, a liquid-form raw material, such as a liquid-form food, is continuously subjected to a process by using a supercritical or subcritical fluid. The method includes a dissolution step for continuously supplying liquid carbon dioxide to a continuously supplied liquid-form raw material to thereby dissolve liquid carbon dioxide in the liquid-form raw material; a holding step for holding the liquid-form raw material, for a predetermined time, into which the liquid carbon dioxide has been dissolved at the dissolution process; a critical process step for holding the liquid-form raw material into which the liquid carbon dioxide has been dissolved under predetermined temperature and pressure conditions to thereby allow carbon dioxide to be a supercritical or subcritical state; and a decompressing step for suddenly decompressing the liquid-form raw material having passed through the critical process step to thereby remove carbon dioxide and collect a product.
In a continuous processing apparatus of the present invention embodying the above continuous processing method, a liquid-form raw material, such as a liquid-form food, is continuously processed by using a supercritical or subcritical fluid. The apparatus includes a raw material supply path or section for continuously supplying a liquid-form raw material; a carbon dioxide supply path or section for continuously supplying liquefied carbon dioxide; a dissolution portion or section for dissolving liquid carbon dioxide supplied through the carbon dioxide supply path in the liquid-form raw material supplied through the raw material supply path; a holding portion or section for holding, for a predetermined time, the liquid-form raw material into which the liquid carbon dioxide has been dissolved; a critical process portion or section for taking out the liquid-form raw material, into which the liquid carbon dioxide has been dissolved, from the dissolution portion and holding it under predetermined temperature and pressure conditions to thereby allow carbon dioxide to be a supercritical or subcritical state; and a decompressing portion or section for suddenly decompressing the liquid-form raw material having passed through the critical process portion to remove carbon dioxide and collecting a product.
Further, a liquid-form substance according to the present invention is a liquid-form substance processed and collected by the above-stated continuous processing method or continuous processing apparatus.
In the continuous processing method and continuous processing apparatus according to the present invention, while the liquid-form raw material, such as liquid-form food and liquid-form chemical, is continuously supplied to the dissolution portion through the raw material supply path, cooled and liquefied carbon dioxide, (hereinafter referred to xe2x80x9cliquid carbon dioxidexe2x80x9d) is continuously supplied to the dissolution portion through the carbon dioxide supply path. A mesh-type filter having fine holes, for example, is disposed at an outlet of the carbon dioxide supply path, and when passing through the filter, liquid carbon dioxide becomes fine bubbles to thereby dissolve into the liquid-form raw material. Of course, a contact efficiency of carbon dioxide and the liquid-form raw material may be increased by other methods, such as a high speed mixer and an ultrasonic wave generator. As is generally known, a solubility of liquid carbon dioxide into a liquid becomes higher as the circumferential temperature is lower. Therefore, while it is desirable that the solution portion is cooled, even if the temperature thereof is the room temperature, a sufficient quantity of liquid carbon dioxide can be dissolved in the liquid-form raw material for a short time. Especially, in a winter season, since the ambient temperature is low, the solubility efficiency is high.
For example, the dissolution portion includes a solution tank, and an inlet of the liquid-form raw material from the raw material supply path and an inlet of liquid carbon dioxide from the carbon dioxide supply path are disposed at a bottom portion of the solution tank, and an outlet for taking out the liquid can be located in the vicinity of a liquid surface at an upper portion of the solution tank. According to the structure, the liquid-form raw material introduced through the bottom portion of the solution tank flows in the solution tank to elevate therethrough, and bubble-shape liquid carbon dioxide also flows in the same direction. Thus, contact areas thereof are extremely wide, so that liquid carbon dioxide can be effectively dissolved in the liquid-form raw material.
Also, the above dissolution portion may be structured such that liquid carbon dioxide is dissolved in the liquid-form raw material by supplying liquid carbon dioxide into the liquid-form raw material flowing through a raw material supply pipe used as a raw material supply path. As described above, in case carbon dioxide is dissolved in the liquid-form raw material in the raw material supply pipe, it is not required to provide a special tank for dissolving carbon dioxide on the way of the raw material supply pipe to thereby miniaturize the whole apparatus.
As a method for effectively dissolving liquid carbon dioxide into the liquid-form raw material flowing in the raw material supply pipe, there are, for example, a method wherein a mesh-type filter is disposed in the raw material supply pipe to allow carbon dioxide to pass therethrough, so that fine bubbles of liquid carbon dioxide are released in the liquid-form raw material; and a method wherein a mixer for mixing liquids is provided on the way of the raw material supply pipe, and liquid carbon dioxide is supplied to the liquid-form raw material on an upstream side than the mixer. Incidentally, as stated above, since the solubility of liquid carbon dioxide into a liquid becomes higher as an ambient temperature becomes lower, it is preferable to cool a portion of the raw material supply pipe where the filter or mixer is provided. However, at this time, it is not always necessary to cool the raw material supply pipe to a specially lower temperature. For example, even if it is the room temperature, a sufficient amount of liquid carbon dioxide can be dissolved in the liquid-form raw material for a short time. Especially, in a winter season, since the ambient temperature is low, the dissolving efficiency is high. Therefore, for example, it is effective only to provide a device for keeping the above-stated portions warm.
The liquid-form raw material into which liquid carbon dioxide has been dissolved at the dissolution portion is sent to the holding portion. The holding portion is structured such that liquid carbon dioxide can act therein on enzymes or microorganisms to be processed in the liquid-form raw material for a sufficiently long time. A temperature of the holding portion is set at a temperature lower than that of the critical process portion, described later, for example, substantially the same temperature as that of the solution portion. As a specific shape of the holding portion, for example, there are mentioned a spiral pipe; a tank having a sufficient capacity with respect to a flow quantity of the liquid-form raw material; a tank provided with a baffle therein; a tank provided with a spiral screw structure on an inner wall surface; and a tank provided with a screw-type structure therein. Or, a tank is divided into two chambers by a partition or like, one chamber on the upstream side may constitute the dissolution portion and the other chamber on the downstream side may constitute the holding portion. In case the holding portion is provided, since the liquid carbon dioxide is sufficiently penetrated into protein for constituting objects to be processed, such as enzymes and microorganisms, for example, even if bacteria is strong, the strong bacteria can be positively killed in the critical process step and decompression step, described later.
Incidentally, as a flow path for sending the liquid-form raw material to the critical process portion, described later, from the dissolution portion, in addition to a first flow path passing through the holding portion, a second flow path which does not pass through the holding portion may be provided separately, so that either one of the flow paths can be selected according to a kind of the process or a kind of an object to be processed. Further, the holding portion may be formed of a plurality of independently operable holding units, and one, a part or all of the holding units may be operated as occasion arises.
The liquid-form raw material into which liquid carbon dioxide has been dissolved at the dissolution portion is sent to the next critical process portion. The critical process portion is held under the condition of a temperature and pressure required for converting carbon dioxide in a supercritical or subcritical state. As such a condition, it is preferable to hold a temperature of 30 to 80xc2x0 C., preferably 30 to 50xc2x0 C. and a pressure of 40 to 400 atm, preferably 100 to 300 atm. Under the condition, liquid carbon dioxide dissolved in the liquid-form raw material is suddenly changed to the supercritical or subcritical state. It is sufficient that a holding time of the liquid-form raw material in the heating tank is at the most in the order of one minute. Therefore, although the temperature is higher than the room temperature, deterioration of a quality of the liquid-form raw material can be suppressed to the minimum.
Next, in the decompression step carried out at the decompression portion, the pressure of the liquid-form raw material subjected to the above process at the critical process portion is suddenly reduced, so that carbon dioxide having penetrated into protein as an active substance of the enzymes is suddenly expanded and protein is destructed to deactivate the enzymes. Also, sterilization of various microorganisms can be carried out. Since carbon dioxide dissolved in the liquid-form raw material is vaporized and volatilized from the liquid-form raw material, the liquid-form raw material can be collected as a product after the process. In such a decompression process, a decompression speed is important. For example, in case the decompression is carried out by using a pressure controlling valve with an orifice, it is preferable to set the decompression speed such that the liquid-form raw material passes through the orifice at a speed of less than 20 msec, preferably less than 10 msec.
Incidentally, as the liquid-form raw material to which the present invention is applied, a fermentation/brewing liquid-form foods, such as raw sake, beer, wine and soy source, various fruit juices and soft drinks, are typically mentioned. Although the fruits juices are generally produced from apples, grapes and various citruses as raw materials, squeezed liquids produced from tomatoes and other vegetables as raw materials may be included. Also, the liquid-form raw material may not be foods, and it may be a liquid-form chemical, such as various infusions, blood formulations and nutrition supply liquids.
As described hereinabove, according to the continuous processing method and continuous processing apparatus of a liquid-form substance of the prevent invention, since the dissolution step of liquid carbon dioxide into the liquid-form raw material and the critical process step for changing carbon dioxide into a supercritical or subcritical state are separated, the respective steps can be extremely effectively carried out, so that the overall process time can be greatly shortened when compared with those of the conventional continuous processing methods and apparatuses. Therefore, a large process tank and a heater for heating the liquid-form raw material are not required, so that the apparatus can be miniaturized. Also, since the temperature setting at the critical process step can be optimized, higher effects of deactivation/sterilization of the enzymes can be obtained when compared with those in the prior art. Further, since the time for which the liquid-form raw material is held in a warm state is short, the flavor of the product is not substantially deteriorated.